Manifold absolute pressure sensor for internal combustion engines

ABSTRACT

A manifold absolute pressure (MAP) sensor for internal combustion engines is disclosed. In the MAP sensor, the top and bottom cases (1, 7) of a sensor housing have a plurality of fitting slots (10) and fitting protrusions (11) at their connection edges respectively and are easily and tightly assembled into a single structure through a mechanical fitting and epoxy bonding process. A plurality of support protrusions (12, 12&#39;) are internally formed on each of the top and bottom cases (1, 7) and support each side of the circuit board (5), with the circuit board (5) being positioned under the sensor member (4) and allowing the pressure inlet pipe (4&#39;) of the sensor member (4) to pass through. A supporting ring (13) and an O-ring (14) are commonly fitted over the pressure inlet pipe (4&#39;) of the sensor member (4) and are closely fitted into the enlarged top end of the pressure inlet port (8).

TECHNICAL FIELD

The present invention relates, in general, to a manifold absolutepressure (MAP) sensor installed in a suction manifold of an internalcombustion engine and used for sensing the internal pressure of acylinder, thus allowing mixed gas to be appropriately fed into thecylinder of the engine in response to the operation of a fuel controlvalve and maintaining a stable operation of the engine and, moreparticularly, to a MAP sensor capable of being assembled through amechanical fitting and bonding process, thus having both a clearappearance and a high vibration resistance free from forming any crackon the sensor housing even in the event of external impact being appliedonto the sensor.

BACKGROUND OF THE INVENTION

As well known to those skilled in the art, a manifold absolute pressure(MAP) sensor is installed in a suction manifold of an internalcombustion engine and is used for auxiliarily controlling suction timingof mixed gas into a cylinder by sensing the internal pressure of thecylinder and outputting a signal, indicative of the loaded condition ofthe engine, to an electronic control unit (ECU) for the engine. Such aMAP sensor thus allows the mixed gas to be appropriately fed into thecylinder in response to the operation of a fuel control valve andmaintains a stable operation of the engine.

FIG. 3 is a sectional view showing the construction of a known MAPsensor for internal combustion engines. As shown in the drawing, thehousing of the known MAP sensor is comprised of two parts, that is, atop case 20 and a bottom case 21 which are integrated into a singlestructure. The bottom case 21, having a pressure inlet port 22 on itsbottom, is provided with a fitting groove on its top surface, thus beingintegrated with the top case 20, with the lower edge of the top case 20being fitted into the groove 23. After the lower edge of the top case 20is fitted into the groove 23, a thermosetting epoxy bond 24 is uniformlyapplied onto the junction between the two cases 20 and 21, thus fixingthe top case 20 onto the bottom case 21. However, the epoxy bond 24 isapplied onto the inside and outside of the junction between the twocases 20 and 21. In order to define a space for the epoxy bond 24 at thejunction, the width of the fitting groove 23 is larger than thethickness of the lower edge of the top case 21, thus allowing the topcase 20 to be moved on the bottom case 21 in the event of the bond 24being not applied onto the junction. Therefore, the known MAP sensor mayfail to be precisely assembled and it is very difficult to assemble thesensor, thus reducing productivity of the MAP sensors. The epoxy bond 24is exposed to the outside of the housing, thus spoiling the appearanceof the sensor. The integration of the two cases 20 and 21 isaccomplished by applying the bond 24 onto the junction between the twocases 20 and 21 and the sensor housing regrettably has a structurallimit with a low vibration resistance. Therefore, the known MAP sensormay fail to effectively resist an external impact and may be easilycracked due to such an impact.

The fitting groove 23 is formed on the top surface of the bottom case21. Therefore, when a gap is unexpectedly formed in the bonding line atthe junction between the top and bottom cases 20 and 21, it is possibleto allow moisture or impurities to be introduced into the sensor housingthrough the gap. In addition, the epoxy bond 24, which is interiorlyapplied onto the junction, generates gas during a hot drying process forthe bond 24 and allows the gas to remain in the housing. Theabove-mentioned moisture, impurities and gas may contaminate and breakthe parts in the sensor housing, thus causing an operational trouble ofthe sensor and reducing the operational precision of the sensor whilesensing the pressure in a cylinder.

In the housing of the above sensor, both a sensor member 25 and acircuit board 26 fail to be stably supported because both the member 25and the board 26 are supported only by a fitting force of the sensormember 25, which is fitted into the pressure inlet port 23 of the bottomcase 21. Therefore, both the sensor member 25 and the circuit board 26may be easily moved and cause a crack at the bonded junction of thehousing in the event of external vibrations being applied onto thesensor.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a MAP sensor for internal combustion engines, ofwhich the top and bottom cases have a plurality of fitting slots andfitting protrusions at their connection edges respectively and areeasily and tightly assembled into a single structure through amechanical fitting and epoxy bonding process, thus completely sealingthe housing, preventing damage of the parts in the housing, improvingthe assembling effect of the sensor, completely hiding the bond from theoutside, improving the appearance of the sensor, giving a high vibrationresistance to the sensor, and allowing the sensor to be free from anycrack even in the event of external impact.

In order to accomplish the above object, the present invention providesa manifold absolute pressure sensor for internal combustion engines,comprising a pressure sensor member having a pressure inlet pipe on itsbottom center, a circuit board electrically connected to the sensormember, a housing receiving both the sensor member and the circuit boardtherein and being formed by integrating top and bottom cases into asingle structure, the top case being integrated with a connector havinga plurality of connection pins, and the bottom case being provided witha pressure inlet port, the pressure inlet port being concentric with thepressure inlet pipe of the sensor member, wherein the improvementcomprises: the top and bottom cases being integrated with each other attheir connection edges, one of the connection edges being partiallyprominent and the other being partially depressed so as to engage withthe partially prominent connection edge; a plurality of supportprotrusions being internally integrated on each of the top and bottomcases and being adapted for supporting each side of the circuit board,with the circuit board being positioned under the sensor member andallowing the pressure inlet pipe of the sensor member to pass through; asupport ring and an O-ring commonly fitted over the pressure inlet pipeof the sensor member at a position under the circuit board; and thepressure inlet port of the bottom case being partially enlarged at itstop end, thus allowing both the support ring and the O-ring to beclosely fitted into the enlarged top end.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an exploded sectioned view showing the construction of a MAPsensor for internal combustion engines in accordance with the preferredembodiment of the present invention;

FIG. 2 is a partially broken sectioned view of the MAP sensor of FIG. 1,with the parts of the sensor being assembled into a single structure;and

FIG. 3 is a sectional view showing the construction of a known MAPsensor for internal combustion engines.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is an exploded sectioned view showing the construction of a MAPsensor for internal combustion engines in accordance with the preferredembodiment of this invention. FIG. 2 is a partially broken sectionedview of the MAP sensor of FIG. 1, with the parts of the sensor beingassembled into a single structure.

As shown in the drawings, the housing of the MAP sensor of thisinvention is comprised of two parts, that is, top and bottom cases 1 and7 which are integrated into a single structure. Integrated with the topcase 1 at one side of the case is a connector 3, which is provided witha plurality of connection pins 2. The top case 1, with the connector 3,defines an internal cavity 6 for receiving both a sensor member 4 and acircuit board 5 therein. The circuit board 5 is positioned under thesensor member 4 and is electrically connected to the member 4.Meanwhile, the bottom case 7 is provided with a pressure inlet port 8 onits bottom.

A plurality of fitting slots 10 are regularly formed on the lower endsurface of the top case 1, while a plurality of fitting protrusions 11are regularly formed on the top edge of the bottom case 7 at positionscorresponding to the fitting slots 10. Each of the fitting protrusions11 is tightly fitted into an associated fitting slot 10, with theoutside wall 11' of each fitting protrusion 11 being brought intofrictional contact with the inside wall 10' of an associated fittingslot 10.

A plurality of support protrusions 12 and 12' are integrally formed onthe top and bottom cases 1 and 7, thus supporting both sides of thecircuit board 5 and maintaining the position of the circuit board 5 inthe housing, respectively. A pressure inlet pipe 4' of the sensor member4, which is concentric with the pressure inlet port 8 of the bottom case7, passes downwardly through the center opening of the circuit board 5,with a support ring 13 and an O-ring 14 being fitted over the pipe 4' inthat order. Both the support ring 13 and the O-ring 14 are tightlyfitted into the enlarged top end of the pressure inlet port 8 and so theoutside walls of the two rings 13 and 14 come into close contact withthe inside wall of the pressure inlet port 8. The support ring 13 holdsboth the circuit board 5 and the O-ring 14 at its top and bottom ends.

The operational effect of the above MAP sensor will be describedhereinbelow.

In the same manner as that described for the known MAP sensor, the MAPsensor of this invention is installed in a suction manifold of aninternal combustion engine and is used for auxiliarily controllingsuction timing of mixed gas into a cylinder by sensing the internalpressure of the cylinder and outputting a signal indicative of theloaded condition of the engine to an electronic control unit (ECU) forthe engine. Such a MAP sensor thus maintains a stable operation of theengine.

In order to assemble the MAP sensor of this invention, an appropriateamount of bond is uniformly applied onto the total length of eachfitting slot 10 of the top case 1 prior to fitting the fittingprotrusions 11 of the bottom case 7 into the fitting slots 10, thuscompletely assembling the sensor. In such a case, the outside wall 11'of each fitting protrusion 11 is brought into close contact with theinside wall 10' of an associated fitting slot 10, thus effectivelypreventing the two cases 1 and 7 from relatively moving at the junctionand preventing the bond from flowing into the outside of the fittingslots 10. It is possible to easily and precisely assemble the sensor,thereby improving productivity of MAP sensors.

INDUSTRIAL APPLICABILITY

In the MAP sensor of this invention, the integration force of the twocases 1 and 7 is doubled since the two cases 1 and 7 is primarilyintegrated with each other by mechanically fitting the protrusions 11 ofthe bottom case 7 into the slots 10 of the top case 1 and are finallyintegrated with each other by the thermosetting epoxy bond. Therefore,the sensor of this invention effectively resists vibrations caused byexternal impact and has a high durability.

In addition, each of the fitting protrusions 11 is tightly fitted intoan associated fitting slot 10 with the outside wall of each protrusion11 being brought into tight contact with the inside wall of anassociated slot 10. Therefore, the sensor of this invention is free fromany introduction of moisture or impurities into the housing even in theevent of a gap being unexpectedly formed in the bonding line of thehousing. The sensor of this invention almost completely prevents thethermosetting epoxy bond from remaining in the sensor housing and so thesensor effectively reduces the amount of gas, which is generated andremains in the housing during a hot drying process for the bond. In abrief description, the sensor of this invention is almost completelyfree from moisture, impurities or gas, which may contaminate and breakthe parts in the housing. Therefore, it is possible to prevent anoperational trouble of the sensor and to improve the operationalprecision of the sensor while sensing the pressure in a cylinder.

The circuit board 5 of this sensor, with the sensor member 4, is stablysupported by the support protrusions 12 and 12' of the two cases 1 and 7at its both sides unlike the typical supporting structure in which thecircuit board is unstably supported by the sensor member fitted into thepressure inlet port of the bottom case.

Another advantage of the sensor of this invention resides in that thesupport ring 13 always presses the O-ring 14 downwardly in the pressureinlet port of the bottom case 7, thus almost completely preventing amovement of the O-ring 14 even in the event of external vibrations beingapplied onto the sensor. Therefore, the sensor is free from pressureleakage from the housing and improves its operational precision whilesensing the pressure in a cylinder.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A manifold absolute pressure sensor for internalcombustion engines, comprising a pressure sensor member having apressure inlet pipe on its bottom center, a circuit board electricallyconnected to said sensor member, a housing receiving both the sensormember and the circuit board therein and being formed by integrating topand bottom cases into a single structure, said top case being integratedwith a connector having a plurality of connection pins, and said bottomcase being provided with a pressure inlet port being concentric with thepressure inlet pipe of the sensor member, wherein the improvementcomprises:the top and bottom cases being integrated with each other attheir connection edges, one of said connection edges being partiallyprominent and the other being partially depressed so as to engage withthe partially prominent connection edge; a plurality of supportprotrusions being internally integrated on each of the top and bottomcases and being adapted for supporting each side of said circuit board,with the circuit board being positioned under the sensor member andallowing the pressure inlet pipe of the sensor member to pass through; asupport ring and an O-ring commonly fitted over the pressure inlet pipeof the sensor member at a position under the circuit board; and thepressure inlet port of the bottom case being partially enlarged at itstop end, thus allowing both the support ring and the O-ring to beclosely fitted into the enlarged top end.
 2. The manifold absolutepressure sensor according to claim 1, wherein a plurality of fittingslots are regularly formed on the connection edge of said top case and aplurality of fitting protrusions are regularly formed on the connectionedge of the bottom case at positions corresponding to the fitting slots,each of said fitting protrusions being tightly fitted into an associatedfitting slot with the outside wall of each fitting protrusion beingbrought into close contact with the inside wall of an associated fittingslot.